The invention relates to systems and methods for ablating myocardial tissue for the treatment of cardiac conditions.
Physicians make use of catheters today in medical procedures to gain access into interior regions of the body to ablate targeted tissue areas. It is important for the physician to be able to precisely locate the catheter and control its emission of energy within the body during tissue ablation procedures.
For example, in electrophysiological therapy, ablation is used to treat cardiac rhythm disturbances.
During these procedures, a physician steers a catheter through a main vein or artery into the interior region of the heart that is to be treated. The physician places an ablating element carried on the catheter near the cardiac tissue that is to be ablated. The physician directs energy from the ablating element to ablate the tissue and form a lesion.
In electrophysiological therapy, there is a growing need for ablating elements capable of providing lesions in heart tissue having different geometries.
For example, it is believed the treatment of atrial fibrillation requires the formation of long, thin lesions of different curvilinear shapes in heart tissue. Such long, thin lesion patterns require the deployment within the heart of flexible ablating elements having multiple ablating regions. The formation of these lesions by ablation can provide the same therapeutic benefits that the complex suture patterns that the surgical maze procedure presently provides, but without invasive, open heart surgery.
As another example, it is believed that the treatment of atrial flutter and ventricular tachycardia requires the formation of relatively large and deep lesions patterns in heart tissue. Merely providing xe2x80x9cbiggerxe2x80x9d electrodes does not meet this need. Catheters carrying large electrodes are difficult to introduce into the heart and difficult to deploy in intimate contact with heart tissue. However, by distributing the larger ablating mass required for these electrodes among separate, multiple electrodes spaced apart along a flexible body, these difficulties can be overcome.
With larger and/or longer multiple electrode elements comes the demand for more precise control of the ablating process. The delivery of ablating energy must be governed to avoid incidences of tissue damage and coagulum formation. The delivery of ablating energy must also be carefully controlled to assure the formation of uniform and continuous lesions, without hot spots and gaps forming in the ablated tissue.
The invention provides device and methods for ablating body tissue. The devices and methods include an electrode carried by a support element made of a material that does not conduct tissue ablation energy. The electrode is made of a material that transmits ablation energy. The electrode has at least one edge that contacts the material of the support element. The devices and methods also include at least one temperature sensing element carried by the electrode adjacent to the at least one edge.
Another aspect of the invention provides systems and methods method for controlling the ablation of body tissue. The systems and methods supply ablation energy to an electrode carried by a support element made of a material that does not conduct ablation energy. The electrode has at least one edge that contacts the material of the support element. The systems and methods senses temperature with at least one temperature sensing element carried by the electrode adjacent to the at least one edge. The systems and methods control the supply of ablation energy based, at least in part, upon temperature sensed by the at least one temperature sensing element.
The invention places the temperature sensing element in an xe2x80x9cedge regionxe2x80x9d between an electrode and a non-electrically conducting support body. The edge region presents an area where electrical conductivity is discontinuous. The resulting rise in current density in this region generates localized increases in power densities, and, therefore, it is a region where higher temperatures are likely to exist. The invention places the temperature sensing element just where localized xe2x80x9chot spotsxe2x80x9d are to be expected. Reliable temperature sensing, which is sensitive to variations in temperatures along the electrode, results.
Other features and advantages of the inventions are set forth in the following Description and Drawings, as well as in the appended Claims.